Mortgage calculator
Extra payment mortgage calculator
Test an extra mortgage payment or recurring extra payments to estimate your payoff date, interest saved, and time saved.
How this calculator works
This extra payment mortgage calculator, sometimes searched as an extra mortgage payment calculator or mortgage extra payment calculator, estimates a standard amortizing mortgage payment from your current balance, interest rate, and remaining term. It then compares the base schedule with a second schedule that includes the extra monthly principal payment.
The formula
The base payment uses the standard amortization formula: P = B × r × (1+r)^n / ((1+r)^n − 1), where B is balance, r is monthly rate, n is months. Each month, interest is added to the remaining balance and the payment is subtracted until the balance reaches zero.
With an extra payment, the same schedule runs but with a larger monthly payment. The difference in total interest and payoff months is what the result panel reports.
Worked example
On a $285,000 balance at 6.75% with 27 years remaining, the base payment is roughly $1,925. Adding $200 extra a month pays $2,125 toward principal and interest — that extra $200 chews through principal faster, shaving years off the term and tens of thousands off the interest. Try $100, $200, and $500 in the extra field to see how the savings scale.
Why extra mortgage payments save so much
Mortgage interest is calculated on the remaining balance every month. In the early years of a loan, almost all of your payment is interest, so principal barely moves. An extra payment attacks principal directly in that high-interest phase, which removes a dollar of principal and all the interest it would have generated over the remaining term. That compounding effect is why even a modest extra payment can cut years off a 30-year mortgage.
Pay extra or invest the cash?
This is one of the most common mortgage questions. The trade-off:
- Paying extra gives a guaranteed, risk-free return equal to your mortgage rate. At 6.75%, every extra dollar "earns" 6.75% by avoiding future interest. It's simple and certain, but it locks up liquidity in home equity.
- Investing the same cash may earn more over long periods (historical stock market averages are higher than today's mortgage rates), but returns are not guaranteed and come with volatility.
Most financial thinking suggests: first clear higher-interest debt, build an emergency fund, and capture any employer retirement match — then weigh extra mortgage payments against investing. Many households do a bit of both.
Before you schedule extra payments
- Check for prepayment penalties — rare on modern U.S. residential mortgages but possible. Ask your servicer or read your mortgage note.
- Specify "apply to principal" when paying extra, so the servicer doesn't push it to next month's payment.
- Keep an emergency fund liquid — home equity is hard to access quickly if you lose income.
- Consider refinancing if rates have dropped materially; that can beat extra-payment strategies.
Related tools & guides
- Using this tool: How to use an extra payment mortgage calculator.
- Deciding to buy at all? See the Rent vs Buy Calculator.
- Full picture of assets and debts: the Net Worth Calculator.
- Higher-interest debt first: the Debt Payoff Calculator.
Frequently asked questions
What does an extra payment mortgage calculator show?
It estimates how extra principal payments may change your payoff date, interest cost, and time saved compared with your current payment schedule.
Is this the same as an extra mortgage payment calculator?
Yes. Use it for extra mortgage payments, mortgage extra payments, or extra principal payments. The important input is the additional amount that will actually be applied to principal.
How do extra payments reduce my mortgage term?
They cut principal faster, so less interest accrues each month afterward — every extra dollar removes itself plus its future interest.
Is it worth paying extra on my mortgage?
Depends on rate, other debt, emergency fund, and investment alternatives. Extra payments equal a guaranteed return at your mortgage rate.
Should I pay off my mortgage or invest instead?
No universal answer. Extra payments are guaranteed but illiquid; investing may earn more but carries risk. Many do both.
Can extra payments trigger prepayment penalties?
Rare today but possible — check your mortgage note or servicer first.
One extra payment a year or a bit each month?
Similar annual effect; monthly is easier to automate and saves slightly more interest by starting earlier.
Important note
This estimate does not include escrow, taxes, insurance, prepayment penalties, ARM rate changes, recasts, fees, or lender-specific payment timing. This page provides educational estimates only and is not mortgage, lending, tax, legal, or financial advice. See our disclaimer.